Fabrication of mixed matrix heterogeneous cation exchange membrane modified by titanium dioxide nanoparticles: Mono/bivalent ionic transport property in desalination

Polyvinylchloride-co-TiO2 nanoparticle mixed matrix heterogeneous cation exchange membranes were prepared by the solution casting technique. The effect of TiO2 nanoparticle concentration in casting solution on membrane physico-chemical properties was studied. SOM images showed uniform particle distribution and relatively uniform surfaces for prepared membranes. Membrane water content was decreased by an increase of additive concentration. Ion exchange capacity was improved initially by an increase of nanoparticle content and then decreased. Transport number and selectivity initially showed a nearly constant trend by an increase of additive content up to 2 wt.% and then decreased sharply by a more additive concentration. Sodium permeability was enhanced by an increase of nanoparticle concentration up to 0.5 wt.% and then decreased by a more additive content from 0.5 to 2 wt.%. Sodium permeability was increased another time by a more increase in additive concentration from 2 to 16 wt.% and then showed a decreasing trend by a more nanoparticle content. A different trend was found for barium permeability. FTIR spectra analysis decisively proved stronger affinity of TiO2 nanoparticles for barium ions compared to sodium ones. A decrease of pH enhances positive charge distribution on nanoparticle surface and improves the flux. Membrane mechanical strength was also improved by an increase of nanoparticle content ratio in the membrane matrix.